We have prepared high-purity methyl dehydroabietate (DHA-Me) from disproportionated rosin consisting of many compounds via methylation and subsequent reaction or recrystallization. DHA-Me was converted into various bifunctional compounds useful as monomers. Among these, 12-carboxy dehydroabietic acid (CDHA) and dimethyl methylenebis-dehydroabietate (MDA-Me) were particularly applicable and both were transformed into corresponding bio-based polyesters or polyamides. The synthesized polymers were cast as thin films, and the resulting films were characterized. In comparison with commercially available super-engineering plastic films, the aforementioned films are more flexible, are more heat resistant, and exhibit high transparency and low density. The porous film formed via the film-making process has characteristics similar to those of an ordinary film.

Abstract

1. Introduction

As growing demands for low carbon society and resource re-cycling society, materials using biomass has been developed. For example, plastics such as polylactic acid (PLA), polybu-tylene succinate (Bio-PBS) and polycarbonate (Bio-PC) are already put into practical use. General purpose plastics, such as polyethylene, polypropylene and polyethylene terephthal-ate are increasingly produced from biomass instead of fossil resources 1).

Biomass materials currently being used include fermented glucose produced from starch which is made from grains such as sugar cane and corn , oil and fat derived from oil plants (fatty acid glycerin ester) and wood-based chemicals such as cellulose, natural rubber and rosin. In addition to having little influence on the environment, biomass materials to be used in the future should be preferably inexpensive and also inedible considering the potential food shortage in the future.

Rosin is an inedible biomass produced from pine-family plants. It has been used for a wide variety of purposes since the days before Christ 2).

Rosin can be divided into three types according to the manufacturing method. (1) Gum rosin is made by distilling raw pine resin extracted from a cut in the pine tree’s bark.(2) Tall rosin is made by distilling crude tall oil, a by-product of pulp production from pine. (3) Wood rosin is made by solvent extracts of chips of pine tree stumps. To produce gum rosin, pine trees are not logged. To produce tall rosin, although pine trees are logged, pine trees grow fast and the forests are renewed in 20 years after planting. Therefore gum rosin and tall rosin are considered renewable chemicals. Rosin has characteristic structures and physical properties (Fig. 1). It is a complex mixture consisting of ten or more types of six-membered-ring tricyclic terpene compounds. Rosin has rigid and bulky structures and is highly hydrophobic. In addition, it has a carboxyl group as a functional group. We have explored methods of derivating a single-compound from rosin. In other words, we considered producing various functional materials from rosin by fine chemical transformation (Fig. 2). This re-port describes transformation of rosin to single-compounds and characteristics of highly functional polymers made from those substances.

Nano Innovation Laboratories Co.,Ltd.Nakazato，Ninomiyamachi，Nakagun，Kanagawa259-0131，Japan

***Original paper（Received November 19, 2015）*

**

Synthetic Organic Chemistry LaboratoriesResearch & Development Management HeadquartersFUJIFILM CorporationNakanuma，Minamiashigara，Kanagawa250-0193，JapanInnovation & Strategy Planning Division Corporate Planning DivisionFUJIFILM CorporationAkasaka，Minato-ku，Tokyo107-0052，Japan

Development of a Transparent and Highly Heat-Resistant Polymer Film Derived from Biomass

Shigeki UEHIRA*，Toshihide YOSHITANI*，Yoshihisa TSUKADA*， Tomokazu YASUDA**，and Kozo SATO***

FUJIFILM RESEARCH & DEVELOPMENT (No.61-2016) 29

2. Preparation of high-purity methyl dehydroabi-etate (DHA-Me) from disproportionated rosin (DPR)

We sometimes use Rosin derivatives produced by Diels-Alder reaction using the conjugate double bond of conjugate resin acid, the main component of rosin. However, in many cases, the conjugate resin acid is easily oxidized and colored, so we use stable disproportionated rosin.

Disproportionation is usually carried out by heating rosin for several hours at 250 to 280℃ under the presence of a Pd catalyst (Fig. 3). During this reaction, dehydrogenation and hydrogenation occur concurrently and dehydroabietic acid (DHA) and dihydro or tetrahydroabietic acid are produced. Normally, disproportionated rosin contains 50 to 60% DHA as the main component (the rest are tetrahydroabietic acid, dihydroabietic acid, both less than 20%, and several types of pimaric acid). We think it is reasonable to extract DHA from

disproportionated rosin (DPR) because DHA is the main component of DPR. In addition, it is preferred that DHA is considered easy to transform chemically because it contains a benzene ring.

Based on that, we examined methods of extracting DHA as a single compound (Fig. 4). Upon examination of distil-lation and recrystallization, it was difficult to purify DHA as it contains a free carboxylic acid. So we esterificated

Fig. 1　Structures and properties of Rosin

Fig. 2　Application strategy of Rosin

Fig. 3　Disproportionation products of Rosin

Fig. 4　Purification scheme of DPR

30 Development of a Transparent and Highly Heat-Resistant Polymer Film Derived from Biomass

DHA to produce a DHA-Me, and we could obtain high-purity DHA-Me by distillation or recrystallization. Finding this pu-rification method was a valuable breakthrough. It made it pos-sible to mass-produce high-purity DHA-Me at low cost. After that, we conducted examinations using high-purity DHA-Me.

3. Preparation of monomer from DHA-Me

We have studied producing a derivative from DHA-Me, as it is necessary to introduce another functional group to utilize DHA-Me as a polymer material. The benzene ring in DHA-Me is considered to have relatively high electron den-sity, indicating that various substituents can be introduced by aromatic electrophilic substitution reaction. At first, in order to clarify the reactivity of DHA-Me, we examined the typical electrophilic substitution reaction on benzene ring. Although DHA has been well known compound from a long time ago and many derivatives have been synthesized, few of them have been commercially available and used in the fine chemical use. The only example we have known is a derivative sulfonated at 12-position carbon which is used as a gastric mucosal protective agent 3) ※1. Generally, aromatic electrophilic substitution reaction on DHA occurs at 11-, 12- and 14-positions. The regioselectivity depends on the type of electrophilic reagent and reaction condi-tions. Fig. 5 shows the outline of the regioselectivity of aromatic electrophilic substitution reaction on DHA-Me we have studied. Reactivity is the highest at 12-position, followed by 14-position. Reactivity is low at 11-position due to steric hindrance. We have found that the reactivity is almost similar to that of p-xylene or m-xylene and those reactions occur under relatively mild conditions.

Hydroxyl group, amino group and carboxyl group can be introduced into DHA-Me as the second functional group. To use DHA derivatives for monomers of polyesters or poly-amides, we thought a carboxyl group is the most favorable. So we examined various methods for introducing carboxyl group into DHA-Me and synthesized several types of dehy-droabietic acid derivatives containing two carboxyl groups (or esters) (Fig. 6). Among those derivatives, we examined the polymerization of 12-carboxy dehydroabietic acid (CDHA) that has carboxyl group directly bonded to 12-position and dimethyl methylenebis-dehydroabietate (MDA-Me) that is dimerized via methylene group at 12-position carbon. As CDHA and MDA-Me are thermally and chemically stable and carboxyl group is in a sterically hindered position, they are expected to have high hydrolysis resistance when they are transformed to esters or amides.

Fig. 6　Conversion of DHA-Me into dibasic acid derivatives

Fig. 5　Regioselectivity of aromatic electrophilic substitution of DHA-Me

※1 Sulfodehydroabietic acid monosodium (Ecabet Sodium Hydrate) is sold as a gastric mucosal lesion improved pharmaceutical.

FUJIFILM RESEARCH & DEVELOPMENT (No.61-2016) 31

4. Polymerization from CDHA and MDA-Me

In the early development stage, we synthesized CDHA via haloform reaction with sodium hypochlorite after acetylation using acetyl chloride (Fig. 7). As environmentally hazardous methylene chloride was used as a solvent and toxic haloform

was made as a byproduct, we studied other synthesis routes and fi nally established the synthesis route using ethyl oxalyl chloride. This route makes it possible to use chlorobenzene as a solvent and employ inexpensive hydrogen peroxide oxidation. Thereby we could prevent producing compound of haloform, and reduce steps in the manufacturing process 4).

Fig. 8　X-ray structural analysis　　Left：CDHA-Cl　 Right：MDA-Me

Table 1　Synthesis of Polyesters

Fig. 7　Synthetic route of CDHA　

32 Development of a Transparent and Highly Heat-Resistant Polymer Film Derived from Biomass

Next, CDHA was led to its acyl chloride derivative (CDHA-Cl), allowing for the isolation high-purity and stable needle crystals.

Fig. 8 shows the result of the single crystal X-ray struc-ture analysis of CDHA-Cl and MDA-Me. It is evident that both compounds are sterically hindered around 12-position and that the molecules are bent. Next, we synthesized various polyesters and polyamides using CDHA-Cl and MDA-Me. Table 1 and 2 show those synthesized polymers and their properties.

5. Fabricationoffilmsandevaluation

We prepared polymer solutions with concentrations of 10 to 15 wt% by dissolving synthesized polymers in a solvent. After removal of small dust and foreign substances by pres-sure filtration, the polymer solutions spread onto glass slides using an applicator and made into films by air blowing and vacuum drying.

We compared the physical properties of the PE-1 and PA-1 films with those of aromatic polyamide (Aramid), polyimide

Table 3　Film properties of PE-1, PA-1, Aramid, PI and PEN

Table 2　Synthesis of Polyamides

FUJIFILM RESEARCH & DEVELOPMENT (No.61-2016) 33

5.4 Low densityAs shown in Table 3, the density of PE-1 is 1.13 g/cm3 and

that of PA-1 is 1.15 g/cm3, much lower than those of Aramid (1.49), PI (1.47) and PEN (1.36). That reason, we suppose, is the polymer chains are bent and the free volume in the polymer fi lm is large. It is supported a by the X-ray structure analysis of CDHA-Cl in Fig. 8.

6. Applicationtofinelystructuredfilms

As described above, we confi rmed that DHA-based poly-mer fi lms are fl exible, high-heat-resistant, high-transparent and low-density. Next, we fabricated fi nely structured fi lms, such a porous fi lm and a honeycomb fi lm, utilizing the self-assembly that occurs during drying process of fi lms.

6.1PorousfilmIn the process of examination of fi lm making methods, we

observed that the fi lms clouded. Upon analysis of the phe-nomenon, we found that a porous was produced in the fi lm. SEM observation of a cross section showed that a porous morphology was formed inside the fi lm (Fig. 12). PE-1 fi lm

Fig. 9　Origami Crane used PE-1 fi lm

Fig. 11　UV-VIS spectra of the fi lms

Fig. 10　Temperature dependence of strage modulus of the fi lms

(PI) and polyethylene naphthalate (PEN) well known as heat resistant plastics (Table 3). Distinct characteristics of DHA-based fi lms include (1) high fl exibility, (2) high heat resistance, (3) high light transmission and (4) low density. Those characteristics are explained in detail in the sections below.

5.1 FlexibilityAs shown in Table 3, DHA-based fi lms are lower in

modulus and strength than other heat-resistant fi lms, so it is suggested they are soft fi lms. On the other hand, they have larger elongation. Those results show that DHA-based fi lms are more fl exible than general heat-resistant fi lms. When PE-1 and PA-1 fi lms are folded, white fold marks are not left and they are not easily cracked or torn. Surprisingly, these fi lms can even be fold into paper crane (Fig. 9).

5.2 High heat resistanceAs shown in Table 3, the glass-transition temperature (Tg)

of PE-1 is 278℃ and that of PA-1 is 350℃ and these fi lms are classifi ed as a super-engineering plastic fi lm just like as Aramid fi lms. The temperature dependence of storage modulus (Fig. 10) shows that the modulus of PEN drops at around 130℃ and that of Aramid at around 200℃. On the other hand, PE-1 and PA-1 keep their modulus high till around Tg. That indicates DHA-based fi lms contain similar self-supporting properties even at high temperature to those at room temperature.

5.3 High light transmissionAs shown in Table 3 and Fig. 11, the total light transmit-

tance of PE-1 is 90% and that of PA-1 is 89%. Showing higher transmittance than those of Aramid and PI or even that of PEN. As haze is small, those fi lms are highly clear and transparent.

34 Development of a Transparent and Highly Heat-Resistant Polymer Film Derived from Biomass

had a two-layer structure with the porous layer on the air side and the uniform layer on the glass interface side (porous lay-er: about 65μm and uniform layer: about 15μm ). Whereas, PA-1 fi lm had only a porous layer.

As shown in Table 4, the density of porous fi lms is about 0.2 g/cm3. This shows that the porosity is about 80%. On the mechanical properties, those fi lms are low in strength. About the temperature dependence of storage modulus, they keep their modulus high till around Tg, just as the transparent fi lms. It shows they maintain high self-supporting properties even at high temperatures (Fig. 13).

6.2 HoneycombfilmHoneycomb fi lms are porous fi lms with the pores arranged

in the shape of honeycomb. Those pores are considered to form by the following mechanism. Water droplets are congealed during the film-making process and they are arranged regularly in the direction of film surface. They serve as a template and make the unique shape on the film surface 5). Utilizing this process, we made a PE-1 honeycomb fi lm (Fig. 14). This fi lm consists of a two-layer structure with 5μm holes layer and a 10μm thick uniform layer. This film also has high heat resistance similar to its predecessors, for example, no deformation is observed after heat treatment at 250℃ for 30 minutes (Fig. 15).

Fig. 13　Temperature dependence of strage modulus of the fi lms

Fig. 14　Scanning electron microscopy Images of PE-1 honeycomb fi lm

　　　　 Left: Top view ,Right: Side view

Fig. 15　Scanning electron microscopy Images of PE-1 honeycomb fi lm after heat treatment for 30 minutes at 250 ℃

Left: Before ,Right: After

Fig. 12　Scanning electron microscopy Images of side view of fi lms Left: PE-1 fi lm ,Right: PA-1 fi lm

Table 4　Film properties of the Porous fi lms of PE-1, PA-1

FUJIFILM RESEARCH & DEVELOPMENT (No.61-2016) 35

7. Conclusion

Selecting inedible rosin as a biomass resource and using it as a starting material, we have produced various types of transparent heat-resistant films. Those films have high heat resistance, high transparency and low density that the conventional petroleum-based plastics don’t have. Although at present these films are still lacking in some aspect, it is considered that there is a high possibility for better per-formance and more functions.

By extracting high-purity DHA-Me as fine chemicals from rosin, an inexpensive mixture, and producing dicarboxylic derivatives with a simple method; we have developed poly-esters and polyamides that inherit the rosin’s structural characteristics (e.g., rigidity, bulkiness and hydrophobicity a) of six-membered-ring tricyclic terpene compounds.

Utilizing these structural characteristics, we will further explore application of these films.

References

1) Bioplastics Market 2012. Yano Research Institute. 2012. 534p.2) Zinkel D. F.; Russell J., eds. Matsu no Kagaku. Hsegawa, Y.,

trans. Harima Chemicals Group, 1993, ISBN 4990024818.3) Wada H. et al., Antiulcer Activity of Dehydroabietic Acid

Derivatives. Chem. Pharm. Bull. 1985, 33(4), p.1472-1487.4) FUJIFILM Corporation. Uehira, S.; Sato, K. JP 5738649.

2015-05-01.5) Iwanaga, H.; Shiratsuchi, K.; Yamazaki, H. Fabrication and

Application of Honeycomb Film. FUJIFILM Research & Development. 2009, no.54, p.38-42.

Trademarks

・Company names or system and product names referred to in this paper are generally their own trade names, registered trademarks or trademarks of respective companies.

36 Development of a Transparent and Highly Heat-Resistant Polymer Film Derived from Biomass